1. Field of the Invention
This invention relates to a multi-speed drive hub for a bicycle, more particularly to a five-speed drive hub for a bicycle.
2. Description of the Related Art
Known five-speed drive hubs generally work with a two-stage epicyclical gear unit. It is known that this type of gear unit permits the reciprocal reversal of transmission ratios, such as drive ring gear/output planet-gear carrier for the speed reduction and drive planet-gear carrier/output ring gear for reciprocal speed increase, with a fixed sun gear in each case. The direct transmission via ring gear or planet-gear carrier results in a transmission ratio of 1:1, and completes the five-stage gear transmission.
To shift such drive hubs, a gear cable is provided, for example, at each end of the hub axle, which gear cable control pawls that displace the drive-side or the output-side coupling gear. The shift control with two gear cables is quite complicated, since the two gear cables have to be united in a shift control fastened to the handlebars of the bicycle.
Also known are two shift controls which are integrated in the hub and which are led outwards on one side via an axle bore so as to be united by a device, that is flange-mounted on the hub axle, to form a one-piece gear-cable control.
In view of this problem, a multi-speed drive hub, in particular a five-speed drive hub, is to be developed in such a way that the shift device is simplified and that shifting with only a single gear cable is possible.